Hello! If both lists are on the same SharePoint site, you can avoid using the Power Automate flow. I will show you both options.
Lookup columns
I have a 'List2' as in your sample.
In 'List1,' I created a lookup column named 'Part1' and referring to the 'Part2' column in the 'List2.' Also, I selected the 'Name2' column as additional.
Thus, the 'Name1' column will be filled automatically on filling the 'Part1.'
Power Automate flow
The 'Part1' and 'Name1' columns are choice ones.
The flow starts on the item creation in the 'List1.'
Get items form the 'List2' filtering them by the value from 'Part1' in the 'Part2' column. If values are unique in that column, it will return an array with just one item.
Finally, update the newly created item in the 'List1' using the value from the 'Name2' column. It will put the action into an 'Apply to each' control automatically but there will be just one iteration as there is just one retrieved item on the previous step.