May you please be more specific in "I am not able to modify the original 
testbench"?

Does it mean
- the file is write protected?
- you are not aware of text editors?
- you don't know the procedure to read in a file in 
verilog/systemverilog? ($fopen, $fscanf)
- this file-read procedure fails at any point?
- you already copied the data from this file into 
filter_in_data_log_force and filter_out_expected, but it doesn't work as 
intented, as the result is X instead of Y?
- there is a problem in including the datafile into matlab?

How can we help, if we don't know, at which point you struggle? Please 
provide us more information.

Basically thats the way to go. The code you provided had some issues. 
After removing them, it is reading the content of the file, doing 
something, and writing it to an output file.
You find the reworked version attached to the post.

The testbench was prooven in modelsim alter 15. The tcl-commands are 
included in the testbench.

You have to check, whether the procedure and timing of applying the data 
and reading it from the filter is done right. Also you have to proove 
the filter output.

[...]
initial begin
    // open files, read input Memory
        $readmemh("P28hex200.txt", IN_MEM);
        filter_output_file = $fopen("Filter_Output.txt", "w");
        
    // Initialize Inputs
        [...]
        
    // Wait 100 ns for global reset to finish
        #100
    
    // release reset
        [...]
    
    // apply data to the filter and read result
        for (i = 0; i < 199; i=i+1) begin
            #1 
            filter_in = IN_MEM[i];
            #8
            $fwrite(filter_output_file, "%h\n" , filter_out);
            #1
            $display("          in %u - out %u", filter_in, filter_out);
        end

    // close file
        $fclose(filter_output_file);
    
    // stop simulation
        #1 $finish;
[...]

Glad to hear, that it helped you. Thanks for the feedback!