Inspect your bike. 8 and 10 mm hex bolts were pretty common at one time on bikes but seem to be increasingly replaced by allen screws. But are still sometimes used for rack and fender attachments

Also you'll probably need a flat or phillips screwdriver for derailleur adjustments

For tours in remote areas also consider replacement spokes which will require a spoke wrench or small adjustable wrench and a freewheel tool and wrench large enough to use it.