Hii
No serum can help in acne scars, this requires procedures like Microneedling PRP , peels or laser like Co2 laser resurfacing all depending upon the types of scars
Pigmentation can be taken care by creams , peels AMS sunscreen
I would advise to Take proper consultation from dermatologist to prevent new acne and to treat the scars and pigmentation
DONT DELAY TREATMENT OR SELF MEDICATE WITH ANY DIY TO PREVENT FURTHER WORSENING
Next Steps
Consult online or your nearby dermatologist