Nema 17 just means it is a stepper motor with a 1.7 inch x 1.7 inch faceplate.
You say they are "used in the farmbot" but nobody here knows what the farmbot is.
It is also not clear why you would use encoders with a stepper motor since one oof the advantages of a stepper is that you can count the steps it makes and so don't need encoders to give feedback.
You need to post more information on your project, remember nobody here knows anything about it.