A J51 Maya template of mine in https://www.cavanmonaghansciencefestival.ie has been Hacked.

Does anyone know how to deal with This.....
It was hacked in Joomla 4 I have updated it to Joomla! 5.3.0 Stable...... and the hack persists
I have moved server, and it is still hacked
Thinking of Eraseing and total rebuild . . . . but does anyone know how / Who can fix a Hack?