Our current network looks like this:

Location 1: 2 Layer 2 switches | subnet 192.168.1.0/24 | Firewall for our VPN
Location 2: 1 Layer 2 switch   | subnet 192.168.3.0/24 | Firewall for our VPN
Location 3: 1 Layer 2 switch   | subnet 192.168.5.0/24 | Firewall for our VPN

We just got a direct fiber connection between location 1 and 2, we also got a new HP V1910 24G layer 3 switch.

I tried to follow the instructions on this site, but I can't get it to work.

I think our network should look like this:

Location 1: HP Switch FIBER to L2 | subnet 192.168.1.0/24 | Firewall for our VPN
Location 2: 1 Layer 2 switch      | subnet 192.168.3.0/24 | FIBER to L1
Location 3: 1 Layer 2 switch      | subnet 192.168.5.0/24 | Firewall for our VPN

So, how can I get routing working on our location 2? It's old gateway was a firewall device on ip 192.168.3.1. I'm thinking on creating a VLAN Interface on 192.168.3.1 on the switch for the Location 2.

But how will I handle that on the HP switch that has a direct fiber connection with that switch?

Please help, I'm not very good with networking.