Question

220 J to kilojoules

350 kj to calories

97.0 kcal to joules

35.0 cal to kilocalories

How do I convert them?

Answer 1

1000 J = 1 kJ is the factor so
220 J x (1 kJ/1000 J) = ?

You see you multiply the value you start with by the factor. You can place the factor as 1000/1 or as 1/1000. Only one way is right. The right way will ALWAYS cancel the unit you don't want and keep the unit you want. For example, you see J in the numerator cancels J in the denominator and kJ in the numerator (the unit you want to keep) stays.

Next is 350 kJ to cal.
1000J = 1 kJ and
4.184 J = 1 cal. Here there are two factors but they work the same way even in long lines of factors from one unit to the next.
350 kJ x (1000 J/1 kJ) x (1 cal/4.184 J) = ? cal
You see the first kJ in the numerator cancels with the first kJ in the denominator of the first factor. That factor converts kJ to J. The J in the first factor in the numerator cancels with J in the denominator of the second factor. That factor converts J to cal which is what you want.

For the others:
1000 cal = 1 kcal
1 cal = 4.184 J

1000 cal = 1 kcal.