Hello.
Diploma in Health inspector is a 3 year UG level diploma course , here basic eligibility criteria is to pass your 10th or 12th class with minimum aggregate 50% (depending upon college/institute) , your minimum age must be 17 year, now you didn't mention institute where you are searching for the availability of this diploma course, so you simply can go for this diploma course by just cracking the entrance exam of institute or national level exam for this diploma course but before this you need to full fill its basic eligibility criteria.
Best of luck.