Repairing Office usually does not require you to have the installation media. That said, provided you have a valid license key, you can download a backup copy of the Office installation files from:
https://products.office.com/en-us/do...726b&tab=ForPC
If you don't have a valid license key, you may not be entitled to use the copy of Office you now have. The mere fact it was installed on the computer when you acquired it makes no difference if the Office licence wasn't transferred as well. You should ask the vendor about that.