Hi Herf,
This is what I found from their website:
Depositing prohibited items:
The following objects are absolutely prohibited during the visit:
luggage / large bags
backpacks /cameras
These [and similar] objects must be deposited before reaching the Office.
A DEPOSIT area free of charge for these objects is available to the right of the façade of the Basilica at ground floor level of the Basilica's premises passed the security check areas. We are glad to provide this service and the objects deposited are supervised by our staff. Because you are entering a very sacred site you must be dressed respectfully, which means shoulders must be covered, long pants for men, and nothing above the knee for women.
Anyone who does not observe these regulations will not be allowed to participate in the visit.
OFFICE HOURS:
Monday – Friday: 9:00 a.m. – 6:00 p.m.
Saturday: 9:00 a.m. – 5:00 p.m.
The last visit always begins at 3:30 p.m. (4:15p.m. from April through September).
Closed: Sundays and Vatican Holydays
Also found this on another site:
Normal sized backpacks and purses will go through security screening, but are allowed – usually.
You should bring your Passport in case they check ID. It’s never happened for me, but it’s better to be safe.
Please note: The above I copied and pasted from two sites. I have not taken the tour and cannot offer a real experience.
https://thecatholictraveler.com/vatican-scavi-tour/
https://wanderwisdom.com/travel-destinations/The-Vatican-Scavi-Tour-Visiting-the-Necropolis-of-St-Peters-Basilica