The MWFA provides a list of grounds with links to Google Maps here.
Each location often has a number of fields. Each club is in charge of the field numbers. Below are the field layouts for the grounds managed by ABH United FC. To find specific field numbers for other fields, try the website for the relevant club (usually your opposition) and look for Field Layout / Our Grounds / etc.
Beacon Hill Oval
Willandra Road, Beacon Hill
(Link for Google Maps)
Tristram Road Oval
Ben Love Place, Beacon Hill
(Link for Google Maps)
Beverley Job Park
Macintosh Rd, Narraweena
(Link for Google Maps)