Hi welcome to HCM
Removal of your appendix is though is a matter of concern but if it is for your benefit , it is good
Exercising for a well shaped body is a welcome move , of course with your doctor's consent . But your are not able to achieve your desired results of 6 packs in lower abs is .a matter of concern
In fact , lower abs tend to be more stubborn than the upper portion in terms of strength and definition. so you need special training .
Traditional ab exercises may work the abs but they do little to burn actual body fat. Fortunately, there are much more effective exercises that carve out a six pack while simultaneously melting off your belly fat.
It also helps boost your immunity
So Dear don't loose heart , there are ways in Yoga and pranayam , which can help you to achieve your goal .
I would like to suggest you to do the as below :-
Kpalbhati Pranayama is a posture of pranayam –Inhale -Take deep breath - Hold - Exhale thrice
Now throw your breath out ,tummy in ,with force , no inhaling .Only exhale . Do 10 times in the beginning .
Take normal breath ,and exhale . Again repeat ten times the Kapalbhati . Increase the number of breaths when you are used to it
Keep palm on the lower belly so that you can be more aware of how your abdomen is moving. .
Inhalation occurs in a deep breath. sending out the air in a burst from the nostrils and constricting your abdomen as you do so.

Now start repeating this at a quick pace. When you do so, the inhalation does not remain deep, but is passive and involuntary, to take in air. What you need to focus on is the quick exhalations. Feel your abdominal muscles contracting when you do so.

Continue for ten such sets. After that take a few regular deep breaths.
It also helps boost your immunity.
2 .Do Agnisar - ,Take deep breath ,exhale . Repeat three times . Now exhale ,start jumping your tummy in and out as long as you can in a breath . when you want a break , take deep breath . and start again . Repeat 3 - 5 times .
First, perform these activities in the presence of a qualified yoga practitioner in order to ensure that you are not doing it wrong.
It should not be practised by pregnant and menstruating women.

Patients suffering from high BP should refrain from doing Kapalabhati.

Ensure that you do it in empty stomach. It can be done at any time in the day except after evening , after meal
If you are very weak and feel dizzy after performing Kapalabhati, discontinue for a while.

. Start small and slowly build until you reach a number that will keep you pepped up.

Hope this helps you solve your query . Take care