As you can see on the plugin page - https://wordpress.org/plugins/updraftplus/ - 1.9.63 is the current version of UpdraftPlus. So, you would not expect an update to be available. To replace the files that hackers have changed with a pristine version, simply de-install and then re-install.
Note that modified plugin files only indicate that hackers have modified the files - they don't indicate how hackers got access in the first place in order to modify files. Most hackers will either a) run scripts to modify every single file they can reach, or b) target files likely to be installed, by searching for popular plugins (UD has over 400,000 users). To find how they actually got in, you'll need to liase with your web hosting company + read the web log files.