Help whit Opensense configuration

[Mago]

Hi,
I have a cisco router only managed by the ISP (i cant access the router), they provide me a pool of public ip addresses 63.xx.xx.64/29
hostmin is 63.xx.xx.65 hostmax is 63.xx.xx.70, but when i surf on internet i go out whit 82.xx.xx.xx.Now i need to put Opensense between the cisco router and mi lan network, i need to configure OpenVPN , and i need to configure Nat for example if i want that the port 3389 opened on the public ip 63.xx.xx.69 point to 192.168.1.18 and the same port of the public ip 63.xx.xx.68 point to 192.168.1.100, wich kind of configuration is more suitable for do this? I heva configured Opensense before but ever whit WAN whit only one public ip Address.i dont understand if i can do this if i connect the wan port of pfsense to the lan of the Cisco ISP Router (as i usually do whit a sigle public address wan)
Any help will be appreciated
Thanks!!