linux: using grep or another command to return the line number of a multiline pattern

I was using the Less command to examine a very large text log file (15 GB) and was trying to look for a multiline pattern but after an investigation, Less The command can only search for single-line patterns.

Is there a way to use grep command to return the number line of a multiline pattern?

The format of the record is something like this in iterations of hundreds of thousands:

Package A
op_3b: 001
ctrl_2b: 01
account_i: 5

Package f
op_3b: 101
ctrl_2b: 00
account_i: 4

Package x
op_3b: 010
ctrl_2b: 11
account_i: 98

CA Package
op_3b: 100
ctrl_2b: 01
account_i: 5

LP Package
op_3b: 001
ctrl_2b: 00
ini_count: 0

ZZ package
op_3b: 111
ctrl_2b: 01
ini_count: 545

QEA package
op_3b: 111
ctrl_2b: 11
ini_count: 0

And what I'm trying to achieve is to have grep or some other command to return the start of the line number when these three line patterns occur:

op_3b: 001
ctrl_2b: 00
ini_count: 0