These are three letters USA callsign postfix. The FCC doesn’t issue completely random postfixes. You may find it helpful to use this practice set as an incremental step in copying full US callsigns. For each callsign postfix, try to head-copy it. First, it is sent in Morse code. Then it is spoken. And finally, it is sent again in Morse code. If you missed it the first time it, the second time allows you an opportunity to learn the word.

73 de AD0WE!