here's a map that ought to be of some help if you opt for the Centennial Trail / Interurban Trail: https://ridewithgps.com/routes/26698763

The other option, through Stanwood, is shorter and kind of fun but you have to either ride a nasty highway into Everett or wander around through Marysville. Here's a map with that route: https://ridewithgps.com/routes/26698776

There are several other ways to cut across to the Centennial Trail - I often ride Norman Rd. and go through Sylvania - and you can find several routes from Snohomish over to the Interurban but the ones I plotted out are probably the most commonly ridden.