A @Owen advised, you will need to use the SFP ports for your WAN connection.
You essentially required a 1000 Base-T SFP.
The Meraki brand SFP is MA-SFP-1GB-TX.
You can find the full SFP datasheet here
The linked SFP should work (Meraki devices accept 3rd pary SFP's) but there's no guarantee on compatibility or reliability.