lost iphone se want to use my old 8plus

Lost iphone se which replaced my 8plus. I have access to itunes, cloud, drive and know id and password. I have a backup on my windows computer from forgetting past passwords. My new service is through cable company and they have sent sim card. I own the phone . When i power it up it reads "iphone unavailable".

1. do i not put the new sim card in yet-I have already taken care of the trusted phone, my credit card and removed it from profile.
2. What steps do I follow or should I call support?
3. I can use my daughters iphone tonight if an apple device is needed

thanks