If the load.php is a file that’s part of your script (I see WordPress has a file at wp-includes/load.php), you can just download a fresh copy of the script from the official website, extract it, find the file that’s missing from your site and upload it to your account.
Just make sure you’re downloading the same version of the script as you’re using on your site. Mixing files from different versions may not be compatible.
All you’ve said so far is that a file “load.php” is missing. Whether that’s from a pre-existing script or CMS, or which version of that script or CMS you’re using, you haven’t said.
So please check what script you’re using and which version, and search the web yourself.