IP Address restriction for Google APIs in Google Cloud Console

I generated an API key for Google Maps and other services for website: naturatravel.ro

Now I would like to restrict Google APIs using IP.
I need IP restriction, else I’m getting:

API keys with referer restrictions cannot be used with this API.

Question1: I need to use the IP of my host (datahost.ro) or that from Cloudflare?

Question2: What IPs I need to use in CIDR notation?

Google Cloud:

IP address restrictions
Specify one or more IP addresses of the callers that are allowed to use your API key. Format >as an IPv4 or IPv6 address or a subnet using CIDR notation.
Examples: 192.168.0.1, 172.16.0.0/12, 2001:db8::1 or 2001:db8::/64

Thanks