find . -name '*_a.abc' | xargs rename s/_a.abc/_Am.abc/
find . -name '*_b.abc' | xargs rename s/_b.abc/_Bm.abc/
find . -name '*_c.abc' | xargs rename s/_c.abc/_Cm.abc/
find . -name '*_d.abc' | xargs rename s/_d.abc/_Dm.abc/
find . -name '*_e.abc' | xargs rename s/_e.abc/_Em.abc/
find . -name '*_f.abc' | xargs rename s/_f.abc/_Fm.abc/
find . -name '*_g.abc' | xargs rename s/_g.abc/_Gm.abc/