You can enable USB debugging mode. by two ways first by mobile settings and second by using combination file. use combination file in case your device is locked or google account locked or FRP locked enable.
USB Debugging Mode – Samsung Galaxy
If you need to facilitate a connection between your device and a computer with the Android SDK (software development kit), view this info.
From a Home screen, tap Apps > Settings > About phone. These instructions apply to Standard mode only.
Tap the Build number field 7 times. This unlocks Developer options.
Tap ABOUT PHONE (located in the upper-left) to go back to the previous screen.
Tap Developer options.
Ensure the Developer options switch is in the ON position.
We provide combination firmware file for Samsung mobiles. for Samsung Galaxy Combination Firmware Files ROM a310 a510s a520l a710k a910f g530 S6 edge g925p S7 g930s g935s g920t g935t S8 g950u S8+ Plus S9 and S9 Plus, Note 9 Note8. Combination firmware is a ROM for developers or engineers they run the device also can fully read and test the equipment of the device.