Your version does not support that character set, I believe it was
5.5.3 that introduced it. You should upgrade your mysql to the version you used to export this file.
The error is then quite clear: you set a certain character set in your code, but your mysql version does not support it, and therefore does not know about it.
so maybe there is a chance you can just make it utf8, close your eyes and hope, but that would depend on your data, and I’d not recommend it.
Open sql file by text editor find and replace all
utf8mb4 to utf8