Presumably you are using either a USB-C to USB-C cable - or of your computer only has USB Type-A ports, a USB Type-A to USB-C cable. Type-A to USB-C adapters should be avoided - as they are uncertified and often cause issues.
If you are experiencing difficulties with your iPad being detected by your computer when connected, if possible try using a different USB port on your computer. Ensure that your iPad is both power-on and unlocked when connecting to your PC.
If you continue to have difficulties, this support page may be helpful with troubleshooting:
If your computer doesn't recognize your iPhone, iPad, or iPod - Apple Support