Here is the formula to get in/sec from motor speed and wheel diameter:
( {Motor RPM} * {Gear ratio} ) * (wheel diameter*3.141) = Inches/second
For a 300 rpm drivebase, it’s either going 43 in/sec (2.75 in omnis), 51 in/sec (3.25 in omnis), or 63 in/sec (4 in omnis). I would recommend you redo these calculations to check my answers and to possible get some decimal places in there for more accuracy
After you’ve found your inches/second, here is the formula to get the time for a certain distance:
Time (seconds) = Distance(Inches) / Speed (Inches/second)
The formulas however will never produce the exact same distance as you plan it to due to external factors (wheel slippage, drive drift, shaft/screw/gear friction, etc.)