Hi Simdolly and welcome to our Forum!
While I cannot tell you precisely where to find scarabs, I can give you a little guidance. First of all, look at Carl's Sims 3 Guide
for maps showing where insects are located in Egypt. These maps have insect icons (shown from the Collection Helper) in the spots where you will find them to be spawned. Secondly, I can tell you, from looking at the Prima Guide, that scarabs are generally found more inland. NOT right on the water. You'll find water beetles in the locations that are right on the water. I hope this is helpful to you!