The standard Rohloff sprocket will be fine. What matters is the width across the teeth. Thorn's reversible aluminium chainring
https://www.sjscycles.co.uk/chainrings/34-thorn-110mm-bcd-5-arm-reversible-single-chainring-332-inch-black is mainly about 5mm thick but is thinner at the teeth to fit a standard single speed chain (8 speed chains will also fit).
However, what you need to look out for is matching the cranks to the chainrings. The Surly chainring is 110 BCD (Bolt Circle Diameter see
https://www.qbp.com/diagrams/tech_content/crank/bcd.html ) so you will need matching cranks. You also need to decide on the crank length. 170mm is a good starting place but, if you have a bike that you are comfortable with then check the distance between the centre of the crank and the centre of the pedal spindle. Cranks and bottom bracket will need to be compatible and the bike should use an eccentric bottom bracket for aducting the chain tension.
Finally, for now, it is advisible to use use a gear inch calculator such as
https://www.sheldonbrown.com/gear-calc.html to compare the gearing of any bike you have with what you propose to order. 38T / 16T is, however, a good starting place as the rear chainglider part for a Rohloff can handle sprockets between 15T and 17T so you can change the gearing by about 6% up or down although this is only about half a gear step on the Rohloff hub.
