1999 Nissan Altima GXE

I was driving my 99 Nissan Altima the other day when all of a sudden I couldn’t go anywhere-engine was running in drive I coasted to side of road got out looked under hood everything looked good then i looked at transmission fluid and was almost none-closed hood called tow truck -they dropped it off- went 1/2 mile down road for trans.fluid came back car had rolled into the street while in park-had to push it back in my drive put trans fluid in started it put in drive still nothing but to put in park while running it would grind. Never no warning of anything .. Please Help ASAP.

Thank You
Dennis