How to filter out segments with underscore

Hello,

I am trying to learn Regex, but still get no clue on how to filter out underscore. Let's say that I have the following segments in Trados and I need to display the segments which contain no underscore characters:

1. Version 2021

2. Contact our customer service by phone (xxx)-xxxxxx

3. Label_Hardware_Firmware

4. OS_Version_Build

5. Manufacturer_ID_Code

6. Tighten the four screws as described in chapter 4 above

7. Save this manual book for future reference

8. Etc.

The original file type is an XML, and the reason I want to "hide" the segments with underscore is because they are DNTs and locked by the client.

Should I create a custom XML file type (and if yes, how)? Or, is there any "direct" regex that I can use?

Thank you.