Merge 2 groups in the same board

When importing our clients database from our google sheet, only the first 20 columns were imported.
To solve this, I have tried to import the data in two phases so that I ended up with 2 groups.
After that, I needed to merge the 2 groups to reconstruct our database table. I was not able to find out how to do that if that even is possible. (This is similar to the operation JOIN in a relational database)
Note that the 2 groups have the same columns (I created the missing columns in each group and left them empty)
Please advise,

If you have two Groups with the same columns, you can merge them (or move all items from one group to another group) by Batch Selecting them then “Move to”.

Use the Move command in the Batch operation toolbar