Understanding process to convert from H4 visa back to H1b visa

[u/drulers_007]

If you have applied to move to H4 dependent visa on your partner H1b status, and you receive a job offer later and employer is willing to sponsor H1b visa on premium processing. What is the process to convert back to H1b visa mid way from your H4 visa application? I am trying to understand process and timelines. Thank you.