Need Help w/ Java Code For Google Sheets

Thank you for the assist -

It's a .xls file from constant contact, imported into Google Sheets.

People have been importing to Constant Contact for years now, using TWO different birthday fields, causing incorrect searches and major problems for the business.

I need to figure out java code to range-lock ONLY the cells in a 40,000 length column which have content, while leaving the other cells open to being pasted into. I then need to apply that code to the range, then cut and paste the other column over. This will remove redundancies while locking existing content. (at least in my head this is the easiest way as I can't seem to find a function that merges the way I need these two columns to) **see image

THANK YOU