how long does it take

Joanna
How long does it take for a higher milk supply to come in when you're only getting drops (not colostrum, the whiter milk after that) and you start pumping every 2 hours for 20 min? A few days or weeks ? She's 3 weeks now but due to her not latching properly bc of a tongue/lip tie and her not getting enough I had to stop and now her formula isn't sitting well so I have decided to Exclusively pump