A for loop has three basic parts:
1) The initial assignment:
someVariable = 0; //for example
2) The test to see if the loop should end:
someVariable < number;
someVariable == number;
are common tests in a for loop.
3) The increment (or decrement):
someVariable++;
someVariable--;
are common
In your program's case, the end test condition is:
1) Wrong, since it needs a comparison operator ==, not an assignment operator =.
2) The range is far too high. If the user enters 70 degrees Fahrenheit, your loop will continue until the temperature reaches 350 degrees Fahrenheit (5 * 70).
That's way past T shirt weather!
Figure out what your assignment requires for a reasonable range, and then set it up with a test comparison ==, not an assignment, OK?