You can perform a factory restore from the Windows 10 login screen. Assuming your issue is a forgotten password, you should be able to boot to the login screen, then hold Shift while tapping Restart on the login screen.

If your tablet doesn't have a physical keyboard, you can hold down the SHIFT key using the On-Screen Keyboard utility, which can be accessed by clicking the Ease of Access icon at the login screen. 
Once the Surface restarts, it should show the following screen:

Click Troubleshoot, then Reset your PC on the following screen.
*Images and technique via: https://www.top-password.com/knowledge/factory-reset-surface-pro-without-password.html