Here's how to convert millimeters (mm) to inches:

* Conversion factor: 1 inch = 25.4 millimeters

Calculations:

* 300 mm: (300 mm) / (25.4 mm/inch) = 11.81 inches (approximately)

* 900 mm: (900 mm) / (25.4 mm/inch) = 35.43 inches (approximately)

Therefore, there are approximately 11.81 to 35.43 inches in 300-900 mm.