howto add a fixed number to id column to make them unique

I have a data table of a network, in this format:
[source id, target id]. e.g.:

1, 2
2, 3

source are users and targets are groups

A program like is capable of drowing a graph from this data.

the problem with my data is that the sources (users) ids are from a db_table, and the targets (groups) ids from another db_table, and they are not unique.
Basically when I have


it means [userid1, group id1] and NOT [userid1, userid1]

The program (gephi) doesn’t understand I have two different types of nodes in my network (from this data).

I thought to change all groups ids from hundreds to 10thousands, e.g:

1 → 10001, 12 → 10012 

and so on.
This way the program can distinguish the two.

Is this a good practise?
Any simple way to do it in the entire group_id column?
Thanks guys

Seems you have a CSV file, you can open it with calc, easily change values in one column with Paste special.

Open the CSV file setting the appropiate options in the import window.
in a cell out of data range enter 10000
Copy the cell Ctrl+C
Select the data id to modify, go to first data id cell, Ctrl+Shift+down arrow.
Menu/edit/paste special/Operation add - Ok.
Delete cell with pasted value.
Save the CSV file.

Thanks, it worked!