Malware? Hacked?

https://www.jojostottphotography.co.uk/blog

Hi clever people!
Here’s the link to the wordpress site in question, had it a little while, but an amateur coding person, so the step-by-steps were great!
About 2 weeks ago i went onto the site to be re-directed / told i needed to download some security – obviously some kinda hack. Having read around as to what to do i can see that simply upgrading isn’t good enough, so i need to find the code / replace the file. If i could be directed towards what steps i need to take, that would be fantastic.

I believe it happened through a needed comments plugin / upgrade that i missed for maybe a week? since upgrading at least the dashboard is now read-able!
Thanks peeps!