How do you calculate mmol? For example, I have 1.018 g of t-pentyl chloride and the answer is apparently 11.5 mmol. Where does that conversion come

How do you calculate mmol? For example, I have 1.018 g of t-pentyl chloride and the answer is apparently 11.5 mmol. Where does that conversion come from?

Another example, I have .371 g of t-pently chloride with the answer being 3.48 mmol.

Also, how do you calculate theoretic yield?