Comparing Unique Values to a Range

I have the following formula

=CONCATENATE (FILTER(boxmod!AC2:AC, {boxmod!I2:AB}=concatboxmod!C2 ))

The intention of this formula is to take a range and compare it to a list of unique identifiers on page “concatmodbox” like so:

CONCATBOXMOD:

C D

1 B

2 BB

3 B BB

In the sheet “boxmod” I have the unique IDS in column AC, and the data to append to them in columns I-AB.

BOXMOD:

I J … AC

B null… 1

null BB…2

B BB … 3

However my formula cannot grab the entire range of I2:AB, so it only works if I write the formula for a single column. Does anyone know how to make a range work in the area {boxmod!I2:AB}?