Good evening Xiaojing and welcome back!
Thank you for reaching out to us.
I would love to help you with this topic.
This looks like a customization of the Filter Bar for your WordPress theme.
If you have not already done so, you might want to read our Themer’s guide to get a sense of how that works.
If you look for a /tribe-events/ folder in your WordPress theme folder, you should be able to see the files to modify.
If that is not clear to you, could you please send me a copy of your WordPress theme and child theme in a .zip file link in a private reply (via Dropbox or Google Drive) so that I can run some tests on my end ?
Please ensure you are using the latest files as found on your actual website.
This way I will get access to any updates you might have made.
Best regards,
Geoff B.