Final answer:
The nurse should instruct the client to ensure adequate protein intake.
Step-by-step explanation:
The nurse in the prenatal clinic should instruct the client to ensure adequate protein intake. The presence of 3+ protein in the urine and a serum albumin level of 3 gm/dL indicate a potential problem with the client's kidney function. Adequate protein intake is important to prevent further damage to the kidneys and help manage conditions like preeclampsia, which can lead to high blood pressure and edema.