I hear how upsetting this is — losing work you were counting on for a Paris exhibit is a genuinely serious problem, not a minor inconvenience.
I am trying to give you answer:
Q1: Turn on Pause updates
Settings → Windows Update → "Pause updates for 1 week," repeatable up to 5 weeks total. This is the closest thing to a full off-switch and is the most reliable option through your exhibit deadline.
Q2: You do not need OneDrive to recover files stored locally on a Windows PC.
If the files are on the internal SSD/HDD, they can potentially be recovered directly from the drive using:
Windows Recovery Environment (WinRE)
Another working PC
A USB-to-SATA/NVMe adapter or enclosure
Disk/partition recovery software
OneDrive is only relevant if the files were actually synchronized to OneDrive.
Q 3: What artwork program? Where were the files normally saved?
Check for autosave/recovery files in your actual art software first — this is the most likely place to find it intact.
For example, in Photoshop: Edit → look for "Auto-Recover"
check %AppData%\Adobe\Adobe Photoshop [version]\AutoRecover