SAP SD , MM or HR ( non technical )

How is SAP SD, MM and HR functional modules for a women, who wants to build a career in SAP after 6-7yrs of gap in IT sector. Is it a prerequisite to have a prior knowldege of the above to begin? Myself being Bcom graduate and have past work experience in Sales dpt as sales admin, customer sales coordinator (SD) logistics as an enduser of SAP. Kindly guide.