I got Tp-Link AX1800 router, but I have some old laptop with old Wifi device. What type Security setting I can do it? WEP?

And for Network Security ID, what kind format I need? I real don't understood: "For 64-bit encryption - You can enter 10 hexadecimal digits (any combination of 0-9, a-f, A-F, zero key is not permitted) or 5 ASCII characters. ", here 0-9, but zero key is not permitted?