Latitude E5430 replacement wi-fi adapter for 5G working - possible?

hi All. Greetings from Thailand where I retired with my wife. Retired means low income, Thailand means apart from my wife I'm in the middle of a community that to all intents and purposes speak unintelligible gibberish. They probably think the same about me! Retired means that even if I need a new laptop there is no money available for one. It is my lifeline to sanity though with a Netflix subscription given to me by my children.

Until a few weeks ago we had an old router that delivered 5GHZ and the lappie could see that and I think somehow used it as connectivity was never a problem, Now however since the old router failed and the ISP gave us a brand-new one the lappie no longer sees the 5GHZ we are paying for and so it won't connect to it. Instead we get 2.4GHZ, pitiful speeds and connection that reapeatedly goes to spinning wheel if you see what I mean. Even YouTube fails and that has to be small bandwidth stuff (technical term I read on Google!)

Can I buy a 5GHZ WLAN adapter and get my local engineer to fit it so I can get the 5GHZ back. I saw a Dell guy made a post asbout buying one on Amazon for an older Inspiron so is there hope for me? Giving me the exact thing to buy for my machine would be helpful because I am pretty amazing on computers - NOT! Take pity someone please!

The ISP say they have no routers that are compatible with my older WLAN - not even old ones, only these super-dooper new ones so although they changed the router f.o.c I might just as well have not bothered them! Sppeds have gone from over 100mbs to 10 - 15 mbs.