Look at the manual here:

https://github.com/usadellab/Trimmomatic

The current trimming steps are:

ILLUMINACLIP: Cut adapter and other illumina-specific sequences from the read.
SLIDINGWINDOW: Perform a sliding window trimming, cutting once the average quality within the window falls below a threshold.
LEADING: Cut bases off the start of a read, if below a threshold quality
TRAILING: Cut bases off the end of a read, if below a threshold quality
CROP: Cut the read to a specified length
HEADCROP: Cut the specified number of bases from the start of the read
MINLEN: Drop the read if it is below a specified length
TOPHRED33: Convert quality scores to Phred-33
TOPHRED64: Convert quality scores to Phred-64

it does not look like it offers the option of cutting a specified number of bases from the end

for that purpose you could use other tools like fastp or cutadapt instead