How to add thousand separator(s) as dot(s) using Regular Expression in numbers without any thousand separator(s) in Trados Studio?

What is the correct Regular Expression to be inserted in "Find What" and the Regular Expression to be inserted in "Replace With" (using Regular Expressions) in Trados Studio Editor (2017 to 2021) in order to add one or more thousand separators as dot(s) in numbers like 1000; 10000; 100000, 10000000; 1000000000000; 20000; 1245; 35938; 5000; 50000 on several Translated Target Segments etc.?

For example a huge number of Target Segments show only numbers:

1000

10000

100000

1000000

10000000

100000000

1235567980

1245

34589

50000

500000

The above number should be modified to:

1.000

10.000

100.000

1.000.000

10.000.000

100.000.000

1.235.567.980

1.245

34.589

50.000

500.000

I found some Regular Expressions in Internet that could add thousand separators, but they do not work in Trados Studio!

Thank you very much for your kind attention.

Best regards.

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