Search the term SLI and you should find your answer as well as the actual steps you need to take in order to make this idea a reality.
He won't be needing an SLI Bridge for mining, those are only required for multi-GPU Gaming PC (
for graphics).
All he need is a mining software that supports both GPU models and each GPU will mine independently.
Not to mention, RTX2060 doesn't support SLI, it's only available for RTX2080/ti