The express 3700 can't be paired to a wifi voice remote, so the only type of remote uses is an IR remote. Roku sells the Simple Roku remote for $14.99. If you want a remote that controls your tv too you'll have to get an aftermarket universal. I suggest the One-For-All urc-7935 streamer remote, works great with roku that accept IR, and can control tv's and soundbars. Here's photo of it be roku tv remote:
They go for $25 at walmart, but can be found on ebay for $10 open box.