Retrieve Marker Coordinates

I need to get Coordinate of specific Marker and Zoom to its position, try this 
aLat := WebGMaps1.Markers.Items[aUserMarkerId ].Latitude.ToString ;
return error 
[dcc32 Error] uMapClient.pas(642): E2250 There is no overloaded version of 'Items' that can be called with these arguments

Ignore, my bad, aUserMarkerId should be an Integer; I had the wrong declaration.