There are many ways you could reply when someone says "Take care."
Here are a few examples:
To start, click on the button to generate 3 random replies. Don't like the replies? Simply click again to get 3 new random replies.
You could also simply say "Thank you" or "Will do" if you don't want to add any additional comments. The key is to be sincere and show that you appreciate the person's concern for your well-being.