how can I find the sprint # for my Samsung phone
It doesn’t really matter. The Sprint number is useless.
You can find instructions in this tip blog How to find your phone's secondary number and stop unwanted calls to that number
(Moderator’s note, quoted content removed as the link suffices.)
Would you share what you’re hoping to use it for? It is not possible for you to get texts on it, or do anything useful with it so perhaps we can help with your end goal?
I wanted to compare that number with the number that was on the text that I sent
If you’re trying to use Samsung Messages, which hasn’t been updated to the latest standards, and doesn’t work correctly with Republic, then certain text messages may indeed come from your underlying number. However texts back to it will fail.