By unit fraction I assume you mean a fraction which has a numerator of 1. Right?

OK. So if we have a fraction with a number which isn’t 1, we make that number into a multiplier. So if the fraction was 3/8 then we can write 3×1/8, which gives us a multiplier and a unit fraction, where the unit fraction is ⅛.

Now let’s consider 2×⅔=4/3, because in the numerator we have 2×2=4. So we take the numerator and write it as 4×1. Then we make the 1 into a unit fraction by replacing the denominator: 4×1/3 or 4×⅓. Another example: 6×⅗=18/5=18×⅕, where the numerator 3 is multiplied by 6 and 6×3=18=18×1. Replace the denominator under the 1 to get 1/5 or ⅕. Got it?