@tarini To give you an idea, this site lists the current outbound ips used by Netsuite:
https://www.nslookup.io/domains/outboundips.netsuite.com/dns-records/
You could give that list to the firewall but it would work temporarily until Netsuite adds or changes the IPs, then you would need to download the list again and update the firewall, that's a very manual process.
Instead, you should instruct the firewall to do update that by itself by making use of DNS lookups. Just point it to the url
outboundips.netsuite.com and it should allow traffic from any of the IPs.