Typically, when you first set up a Mac, you will use the Setup Assistant to first create the initial Administrator account (which you do not want to name the same as your old Mac's user account,) and then, follow through the set up process to where you would use it to migrate your user account from the old Mac to the new one. This would result in two separate user accounts: an Administrator account, and your user account.
It looks like you did create the initial Administrator account with the same user name as your old Mac's. This is why you now have a second account with the same name and ending with "_1." The issue as you now see is that the permissions on each account do not allow access between accounts. Fixing this is not a simple copy & paste between accounts.
My suggestion, especially if you have not erased your old Mac's drive, is to start over by following the steps in these support articles.
Use only one of the following articles to erase your new Mac's internal drive, depending on what type of CPU that it has:
Next, use this article to reinstall macOS on the new Mac:
Finally, use this last article to migrate your user data from your old Mac to your new one:
Ref: