VBA copy value from array to another array - Type mismatch error

Hello,

I just noticed a mistake and thought I found the solution myself already (edits in red), but the same error pops up

I need help with the following code.

Dim pitch_arr As Variant

    Dim i As Long
    Dim x As Long
    x = 1
    For i = LBound(screw_data_arr) To UBound(screw_data_arr)
        If screw_data_arr(i, 1) = 3 Then
            Debug.Print screw_data_arr(i, 2)
            pitch_arr(x) = screw_data_arr(i, 2)
            x = x + 1
        End If
    Next i

screw_data_arr is an array that is created in another Sub (Public screw_data_arr As Variant) from a table in one of my worksheets.
It consists of 75 rows and 5 columns.
Column 1 contains different bolt thread sizes, column 2 the respective threads per inch for that thread size (also referred to as "pitch").
So, in my example, if I search for the thread size of 3, it should write all the thread pitch values (4,8,12) for that thread size into the array pitch_arr
Upon executing the code, I get a Type mismatch error inside the If statement.

See the example table below:

Size	Pitch
2.5	4
2.5	8
2.625	12
2.75	4
2.75	8
2.875	12
3	4
3	8
3	12

Never mind. I changed the array declaration as follows: Dim pitch_arr(1 To 3) As Variant.
Now it works.
However, how would I do it if I wanted a dynamic array of unknown size?

Edit//
Found a solution with ReDim Preserve