First of all, you can log it out to see what is happening:
console.log('***' + mystar + '***')
console.log('***' + 'This is the start. This is the end.' + '***')
The first line will show what you are making and the second line what it is supposed to be. (The *** stuff is just to show the beginning and end clearly.)
You also didn’t name your variable correctly.
Read the instructions closely. Details matter. At least to computers they do.
Please don’t just give the answer, especially with the curriculum. This is a learning platform. We try to guide them to the answer, not give it to them to cut and paste.