Using array to make 'for' loop more efficient

hi all!

i have a workbook (redacted) attached that:

1. takes user input on Sheets("Input")

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2. takes list of trades from Sheets("Data")

3. pastes list on Sheets("Output") then loops through and deletes irrelevant trades (deleting rows where column A != BK OR left(3) of column C != ST)

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so we only want to be left with trades that match both BK and ST

there are typically ~62k rows of trades and the loop/delete row process is very slow...i've read about ways to increase the efficiency of this process using an array but don't quite understand how to execute this. any pointers?

cheers

sampleSS.xlsx