Hi, you have mentioned, "Now I want to create a VPN connection between azure vnet and azure vm". I am assuming you want to setup VPN to access Azure VM from an on-prem network? Your subnet must be overlapping.
You can try like this.
Address space :10.0.0.0/16
Subnet1: 10.0.1.0/24
Subnet1: 10.0.2.0/24
I hope this will help. It does not help then provide me more details.