Happy New Year to all

No sure what the right number is to configure my motors on the motor tuning dialog in Mach3. I have ball screws with 10mm pitch and I will use 1/8 microstepping. I convert the 10mm to inches which is 0.39" and I use the following:

8 x 200 = 1600 x 0.39" = 624

Is the 624 the right number?

No you will be 4064 if you are direct coupled.
1 inch is 25.4 so a 10mm pitch screw will have to turn 2.54 times for an inch, so 200 x 8 x 2.54 = 4064 steps per inch.
Hood

Thank you Hood, I'm direct coupled so I will use 4064