2 answers
Hello @VEDASRI PONNANA
I see you can't find the 'Salesforce' license while creating a new user for your Trailhead challenge.
1. Checkorg- Make sure you are in the right Trailhead Playground(Enterprise/Developer edition).
2. Go to setup-->Company Information -->Company Information-->User Licenses. Check if 'Salesforce' licenses are available.
3. See if the challenge accepts 'Salesforce Platform' or 'Standard User' instead.
4. If it's missing, create a new Trailhead Playground and try again.