These are part of the Rouge National Urban Park and is called the Twyn Rivers Area.
The trails are poorly marked. Here's a link to the trails https://www.pc.gc.ca/en/pn-np/on/rouge/culture/histoire-history/twyn
. There is no parking on Twyn Rivers. You need to park in the parking lot east of Maxwell's Mill and walk back. Get coordinates before you go because it is not signed as a trail head.
The authors of 'Hiking the GTA' has a good write up of Maxwell's Mill. See https://hikingthegta.com/2016/11/23/maxwells-mill-rouge-park/
The only think I couldn't figure out was the source of the head water for the mill. The Hiking article says the remains of the dam are by the parking lot but that doesn't make any sense to me.