Here's how to convert centimeters (cm) to millimeters (mm):

* Understanding the Relationship: There are 10 millimeters in every centimeter.

* The Conversion: To convert from centimeters to millimeters, you simply multiply by 10.

* Calculation: 387 cm * 10 mm/cm = 3870 mm

Therefore, 387 cm is equal to 3870 mm.