Elementary Autonumber Question

[jdeland1 at comcast.net]

I inherited some files with autonumbering for a Caption style like this: M:Fig. <$chapnum>\+< >< ><n+>:\  , which results in displayed text such as this: Fig. 3-1: 

But the spec calls for the result to be Fig. 3.1: 

I'm not sure from the Help file what the angle brackets do, but I can't seem to get that "." in place of a "-". 

A little help?  And thanks in advance.