How do you migrate Windows 10 from HDD to SSD without losing any data

The process is called cloning but it can be hit or miss especially if your SSD is smaller than the HDD.

The method that always works is to create a image backup of the HDD to an external hard drive using Macrium Reflect Free. Then restoring that image backup to the SDD. Since your SSD is smaller than the HDD, you will need to investigate what additional steps you will have to take.

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@Stanley0628  Building on the answer from @nyc10036 above, I'm a heavy user of Macrium Reflect, and the Free version will indeed serve your purposes here.  This is Macrium's KB article about how to clone a disk, and Steps 4 and 5 show how to resize partitions in order to cover cloning to a smaller disk (or a larger disk if you want to upsize partitions as part of the clone itself).  If you would instead be capturing an image backup to an external drive and restoring it onto the SSD because you don't have a way to attach your source and destination disks simultaneously, then Steps 4 and 5 of that article also apply to the image restore wizard, except the option is called "Restored Partition Properties" rather than "Cloned Partition Properties".

Additionally, before you perform the disk swap, create bootable Rescue Media onto a flash drive within Reflect and confirm that your system boots from it successfully AND that it can see your internal storage and your external storage if applicable.  The reason is that if you will be performing an image capture and restore, you'll be performing the latter within Rescue, but even if you're performing a clone, if the new disk doesn't immediately boot, you'll want to boot into that Rescue Media and run the Fix Boot Problems wizard.

And lastly, if you perform a clone to the new disk while it's attached via a SATA to USB adapter or something, note that you must install that disk internally before you will be able to boot from it.  Sorry if that sounds obvious, but some people have tried to test boot their cloned disk while it's still connected via USB, and Windows does not allow itself to be booted from a USB storage device (except Windows To Go, but that's a special setup).

Since it would appear that the LT is capable of NVMe SSD and HDD you could use Dell's process to backup the OS to and external USB (32Gb or larger) then do a selective boot to USB after installing the M.2 NVMe and install the OS to the M.2 drive. BUT, if what you have is a 2.5" SSD then you won't be able to migrate since the LT only supports one 2.5" drive. I would suggest that if this is the case, return the 2.5" SSD and get a M.2 NVMe SSD then your data would not need to be migrated it would simply be a second drive in the system.

Wishing you luck...

https://www.dell.com/support/manuals/us/en/04/vostro-14-5481-laptop/vostro_5481_setup_specs/storage?guid=guid-f02ff57d-ecf7-465e-9046-8d7077dda9f0&lang=en-us

@HarryIndia  Thanks for reporting back, and great news!

Thank you! I followed your instruction and got the SSD successfully cloned from a hard drive. I got an error code 0xc0000e after I 'Diskpart> clean' my hard drive (more info here) and loaded windows from the SSD. However, I made a Rescue Media USB earlier as you instructed and it fixed my laptop. DO NOT SKIP this USB Rescue Media step!

Hello,

The easiest way is to get a external hard drive and copy everything to that drive they copy it back to the internal drive.

Very simply to do.

Hopefully you've found a solution in all this time... if not, I would recommend buying and external inclosure for the old drive and HOPEFULLY you've run the backup restore for the Dell laptop so you can re-install Windows 10. If not the entire process can become very complicated very quickly. Good luck...