That should do the job:
for i in *.cfg; do
sshpass -p "password" scp ${i%.cfg}.txt username@${i%.cfg}:
done
The password is passed to scp using sshpass following How to pass password to scp? – remember to secure the file against unauthorized read access with chmod 700 if you store a password in plain text!
I got a little bit confused what file you want to send here, I understood there's e.g. a file ABC123.txt that has to be sent to host ABC123, so I just stripped .cfg using Bash Parameter Expansion and added .txt.
As user@host: defaults to user's home directory I removed the path.
A little more secure approach (thanks to pa4080!) would be to make it a script and give it the passwort as the first argument, this way you don't need to store it in plain text:
#!/bin/bash
for i in *.cfg; do
sshpass -p "$1" scp ${i%.cfg}.txt user@${i%.cfg}:
done