Copy items to Lookup Column - Sharepoint List

Hi!

I'm new to Sharepoint lists and am trying to migrate my data from excel. Some of the excel columns are lookups, which I would like to emulate in the list and I have managed to create new lookup columns in the list, but these are not populated with my old data. Is it possible to copy data from one column to a lookup column in the same list automatically?

As I have over 10,000 lines and multiple columns which need to be populated, is there a way to do this other than using the grid view edit (copy and paste) method?

Thanks in Advance