First thing to do is to upgrade to a currently supported version of OpenWrt. 19.07 has been EOL and unsupported for many years and contains many known security vulnerabilities.
Once your device is upgraded, you need to figure out which chipset is inside that device. If you search the forums, you will see threads about USB WiFi adapters and how to determine the appropriate drivers. Keep in mind that some will not be supported at all and others may be supported only in STA (client) mode.