OK, if I were you I would walk, it's only 1.3 miles. but if you want to do public trans, here's what I found:
Walk to Washington St & Powell St
Cable car - POWELL-HYDE - Cable Car - Direction: Powell & Market
Arrive Powell St & O'Farrell St
Walk to 181 3rd St
OR:
Walk to the corner of Stockton/washington
Take Muni Bus #45 (caltrain) to 4th and mission
Walk to 181 3rd st.
I used transit511.org and googlemaps.com for these directions. If you use google you just need to click "get directions" then when they come up click on "take public transit"