MySQL to Copy row to row in Wordpress database

I'm switching between two shopping cart plugins and my product prices did not transfer over well. I'm wanting to copy the price from one row of the postmeta column to another.

These 2 select queries work:

SELECT meta_value FROM `postmeta` WHERE meta_key= 'max_variation_regular_price'
SELECT meta_value FROM `postmeta` WHERE meta_key = '_price'

But I cannot figure out how to use a insert or update operator to copy the values of '_price' into 'max_variation_regular_price'

Thanks for any and all help and suggestions!