To determine how many mL of the medication you need to administer to achieve a dose of 750 mg when the concentration available is 250 mg/mL, you can use the following formula:
\[ \text{Volume (mL)} = \frac{\text{Dose (mg)}}{\text{Concentration (mg/mL)}} \]
Substituting the values:
\[ \text{Volume (mL)} = \frac{750 \text{ mg}}{250 \text{ mg/mL}} = 3 \text{ mL} \]
Therefore, you will give 3 mL of the solution.