Hi, I am using the pulumi and I have tried the organization for my stack, now I want to switch to personal as I am the only one who use the pulumi at this time. how can I switch back to the personal account?

You can do this through the console: https://www.pulumi.com/blog/stack-transfers/

To use your personal namespace rather than your organization one, either remove the organization prefix, or use your account name as the prefix. For example,

pulumi stack select dev
pulumi stack select myaccount/dev # same as previous line

So if you want to destroy all the resources in a particular org stack, then recreate them in a personal stack (which has pretty much the same result as Anthony's more powerful technique above), you could do this:

pulumi stack select myorg/dev
pulumi destroy
pulumi stack select dev
pulumi up