The best way is to use OpenVPN, WireGuard or ZeroTier. If your shop router has OpenVPN server built in, enable that, and install the OpenVPN client on your Shield. I believe ASUS routers will walk you thru the process, but you may need to look on youtube for your router brand on how to set up OpenVPN.
Otherwise, you will need a computer with WireGuard or ZeroTier (free for community version) on it and the install the WireGuard or ZeroTier client on your Shield, then you should be able to view your cams at home. Note that you could install OpenVPN on a Windows computer too, but it's a bit complicated.
I think ZeroTier would be the easiest to set up, but look thru youtube for it and WireGuard.
You may need a
DDNS service to keep track of your office IP address (if you don't have a static IP address) in case it gets changed, there are free and paid ones, like duckdns, noip (free version requires you to renew monthly...you get an email and it's easy), etc.
Edit: forgot to mention IPCamTalk has a free one too:
IP Cam Talk DDNS
