Help with tyre sizes

Hello fellow pedalists

I've a question about tube sizes, as one of my bikes has a weird size. Weird to me anyway! It's a 2017 Cannondale Bad Boy 1.

The tyres are Schwalbe G-One Performance, 650x40c, folding, on Bad Boy C1, 650b, double wall rims. And it's making my brain hurt working out what inner tubes I need.

I've ordered some 27*1 3/8-1 3/4 tubes as they're about 35mm to 44mm. I think. But.

Not really sure what I'm doing tbh!

Any suggestions, please?

Thanks