Adjust headlines to h2

[manter]

Hello,  some of the sections in my theme have h6 and I need to make them h2. Example attached. What would be the easiest way to edit them to h2?

Page:

https://holycup.lt/

Thank you!

[manter]

Hello, thank you. It's quite hard for me to locate the files in the code. Maybe you have any suggestions how I can search for them?

Thank you!