To make a strong password It should have the following

• Has 12 Characters, Minimum: You need to choose a password that’s long enough. There’s no minimum password length everyone agrees on, but you should generally go for passwords that are a minimum of 12 to 14 characters in length. A longer password would be even better.
• Includes Numbers, Symbols, Capital Letters, and Lower-Case Letters: Use a mix of different types of characters to make the password harder to crack.
• Isn’t a Dictionary Word or Combination of Dictionary Words: Stay away from obvious dictionary words and combinations of dictionary words. Any word on its own is bad. Any combination of a few words, especially if they’re obvious, is also bad. For example, “house” is a terrible password. “Red house” is also very bad.
• Doesn’t Rely on Obvious Substitutions: Don’t use common substitutions, either — for example, “H0use” isn’t strong just because you’ve replaced an o with a 0. That’s just obvious.

Or just go here and do it

Strong Password Generator