What data mgt solution to implement? Thousands of autocad and SW files

Hello,

We just merged with another small company. And now we need to decide how to proceed with the combined thousands of cad files.
Any tips much appreciated, thanks in advance!

Company A:
- several thousands of Solidwork files, both assemblies and parts. With extensive file referencing
- stored inside an old 2004 Solidworks PDM system (I think EPDM from that year)
- last engineer left 4 years ago. No new development work created since then.
- Installed Solidworks version (and PDM) is from 2004. Disks and license nr has been lost some years ago

Company B:
- several hundreds of DWG, STL, OBJ and PDF files.
- we outsource engineering work, but have 4 prod mgr's who use the files (viewing)
- no PDM system, Windows Explorer is our file mgt system
- no CAD software, we use viewers and communicate changes to the freelance engineers via email and phone

Our requirements:
- Wish to create one library/folder structure of all engineering files
- All new engineering work to be outsourced to freelancers / outside engineering companies
- In-house we have 4 product mgr's who will view the files. Preferably also able to make simple annotations for the outside engineers
- We are a small team, no need for complex check-in/check-out or workflow functionalities

Our question: what type of solution should we look at?
What I have come across:

• Staying with Windows Explorer/file mgt system - is perhaps to simple given the number of files.
• Solidworks EPDM - seems not to play nicely with non-solidworks files + outsourced engineering collaboration work probably needs very expensive add-ons/extensions
• DDM PDM - can handle various CAD file formats but getting Solidworks EPDM data into it appears to be a tough multi-day consulting job. And is not designed to easily handle outsourced engineering collaboration functionalit
• Grabcad Workbench - simple and collaboration is build-in. But appears to be End-of-Life as most recent Solidworks 2018/2019 files are not supported
• Kenesto - cloud based PDM, not researched yet
  
• Onshape - cloud based CAD and PDM. But we do not need CAD functionality in-house
• ...?....

Any suggestions more than welcome!