Good day!
The Catalyst 3750 is a Layer 3 switch and is not suitable for VPN termination.
You need the other device (router, PC or server) as VPN client.
Can you use a server located on another site?
I am certified network engineer MTCTCE/MTCNA having over 10 years of experience in configuring, maintaining and troubleshooting of enterprise network devices, firewalls, Linux servers.