Is there a way to calculate hours worked on a fillable where one field says "TIME IN", the other says "TIME OUT" then it would automatically calculate the hours in the next "HOURS" field

Certainly, but time calculations in JS are quite complex.

See these tutorials about the subject:

https://acrobatusers.com/tutorials/working-with-date-and-time-in-acrobat-javascript

https://acrobatusers.com/tutorials/working-with-date-and-time-in-acrobat-javascript-part-2

https://acrobatusers.com/tutorials/working-with-date-and-time-in-acrobat-javascript-part-3

I've developed a script that can help you set up this kind of calculation very easily, without having to write any code yourself.

You can find it here: Custom-made Adobe Scripts: Acrobat -- Calculate Time Differences in a Worksheet