Dell EMC Configuration Guide for the S3100 Series 9.14.2.4

If you know the interface index, use the following commands to find the interface number.

DellEMC ~ $ snmpwalk -v 2c -c public 10.16.206.127 .1.3.6.1.2.1.2.2.1.2 | grep 2097156
IF-MIB::ifDescr.2097156 = STRING: TenGigabitEthernet 1/1

DellEMC ~ $ snmpwalk -v 2c -c public 10.16.206.127 .1.3.6.1.2.1.31.1.1.1.1 | grep 2097156
IF-MIB::ifName.2097156 = STRING: TenGigabitEthernet 1/1

You can use the show interfaces command to view the interface index.

DellEMC#show interfaces gigabitethernet 1/21
GigabitEthernet 1/21 is down, line protocol is down
Hardware is DellEMCEth, address is f8:b1:56:82:de:70
    Current address is f8:b1:56:82:de:70
Pluggable media not present
Interface index is 2097156