1994 Ford F-150 about my 94 Ford F-150 flareside

I was driving down the road an I was in third an went to put it into 4th an herd something when I put it into 4th after that I let out of the clutch to go an it acted like it was in neutral so I tried to put it into 3rd and same thing so I went to 2nd an it went I didnt hear any grinding when I put it into 2nd but I was able to drive truck home using 2nd and 5th gear someone told me I broke a fork in the shifter but how or what is it to replace or fix my problem