You updated the Core plugin to the latest version, but the version of the theme is old. Never update the XStore Core plugin without the theme update. Always check the changelog and the necessary version of the Core plugin for your theme version https://xstore.8theme.com/update-history/ Now you need either downgrade XStore core plugin or upgrade theme using auto-update (Dashboard > Updates) or manual FTP way – http://xstore.helpscoutdocs.com/article/63-theme-update
Do the backup of your database and files before starting the theme update.
Also, before the theme update to 6.1.3 version, you need to be sure that PHP version is 7.0 or 7.2. Read more in the changelog, a lot of new features were added in new versions of the theme.
If you need help with the update, provide us with FTP access + confirm that you created the backup.
