Click on the Desktop to get Finder's attention, and then cmd+K to open the Go To Server dialog. Here, the syntax is one of these, where the n's are the ipv4 address, and an example of a Synology DiskStation serving content as Apple File Protocol.
smb://nnn.nnn.nnn.nnn/Share
smb://user:password@nnn.nnn.nnn.nnn/Share
afp://DiskStation.afpovertcp.local/Share
Additionally, if you see the server name in the Finder Window's sidebar under Locations, you can click on that and the first time, waste no time clicking the Connect As… button in the Finder to configure it with username/password and share to mount. Once you have done that, just selecting the server name in the Locations will automatically mount the share for selection in a Finder window.
In the Finder proper, a colon in a filename is illegal as it is an AppleScript path separator, and will be automatically changed to a forward slash for each colon occurrence.