What to run
Open CIDR Calculator. It stays in the browser.
How to read the result
Network is the first address of the block. Broadcast is the last.
First and last usable sit inside, and usable count excludes those two on normal subnets.
Netmask is the dotted form of the prefix. Wildcard is the inverse mask some ACLs want.
What to open next
Open What Is My IP if you are checking whether your address sits in a range you were given. That result is from Cloudflare.
Compare by hand. The calculator does not test membership of a second IP unless you re-enter that IP with the prefix.