Grammar Check for a Sentence About Sand Dunes for a 6-Year-Old

Your sentence is almost correct but can be improved slightly for clarity and grammar. Here's the corrected version:

"Wind picks up sand and carries it to new places. That’s how it makes sand hills called dunes and barchans."

Explanation:

• Removed the word "And" at the start of the second sentence because starting with "And" is less formal and can be omitted here for clarity.
• Removed the comma before "called dunes and barchans" because it is not necessary.

This version is clear and easy for a 6-year-old to understand.