When buying eyepieces for telescope, how do i know whether or not the eyepiece's gonna fit into the telescope?

what kind of features do i have to look for? i usually see numbers like 2.4", 5", 7", etc... and i dont know what they mean. Im trying to buy new eyepieces for my new telescope and dont know what to look for? my telescope brand is Meade 60mm (2.4") 700mm focal length refractor. Please Answer and thank you