How Do You Count?

Here's a handy method that uses the standard piece values: queen = 9, rook = 5, bishops and knights = 3, pawn = 1 As you calculate your line, you start with a value of 0. If you capture a rook, for example, you add +5 to your running count, If your opponent captures your bishop, you add -3. Through the entire sequence, you only need to keep track of one number.

The following book deals extensively with the topic of 'counting' when trading/exchanging pieces....it will teach you everything you need to know...
Back to Basics: Tactics By Dan Heisman. Focuses on the process of analyzing and calculating chess tactics, and introduces the essential concept of 'counting' material during exchanges and combinations. With its detailed explanations, many consider this to be one of the more instructive books on tactics for the novice player.
also check out...
https://www.youtube.com/results?search_query=exchanging+pieces+chess
https://www.youtube.com/results?search_query=exchanging+pieces+chess
Improving Your Chess - Resources for Beginners and Beyond.....
https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond
https://www.chess.com/blog/RussBell