Centering a thumbnail gallery

Sorry, here’s the page i’m working on;

https://www.lcrephoto.com/exteriors/

The only thing you can do (if you want to keep 3 columns) is something like this:

.ngg-galleryoverview {
    margin-left:225px;
}

“text-align:center” doesn’t work & “float:center” doesn’t exist ??

https://www.ads-software.com/support/topic/center-thumbnails-read-pls-ive-look-for-other-solutions?replies=8