I am thinking it will boil down to just this much

Steps = Length / 0.003121
OR
Steps = (Length * 1602) / 5

About the question of your numbers with decimal point, PBP has no native floating point support. So, you have to coax your values into a fixed decimal base or maybe use the FP support addon with all its bells and whistles.

The method above is suitable for plain integer math and can be used with PBP below PBPLong version too.