If a retail store manager starts his career with a new company but the staff's are not co-operating, obeying his orders, what steps he should take?

Stop giving orders.  You're only undermining your own authority.

Your staff have no respect for you, and as a consequence you have no authority.  In the short term the store will operate quite well without you (a store doesn't stop working just because there is no manager for a couple of weeks). 

Respect has to be earned. Task1 is to respect your staff.   From your question, I suspect you have arrived in the new store and started giving orders without understanding how the place works.  So, show some respect for your staff: ask them how they do things, how things could be done better, and what you can do to make their jobs easier.  Get to know your people. 

Task2  is to work harder than everybody else, and be more competent than everybody else.  Get there first and leave last, and be super-competent at the administrative part of your job.  Spend a day working on the tills, a day shifting boxes in the warehouse, and so on. This will help you to get to know your people.

Task3.  Be more modest.  Every morning and every night look in the mirror and say "I lead a team of people in retail store.  That means I am their servant.  It is my job to make their lives easier, so that we can all serve our customers and the company better.  As the servant of my staff, how can I make their work lives better today/tomorrow?"

Task4.  Find out about your predecessor, and any other possible successors. It may be that somebody popular in the store was expected to take over as manager. 

A really good store manager should spend most of the day doing whatever you want - drinking tea in your office, boosting sales by walking the floor, thinking about improving the business, whatever you like.  Yes you will have a few hours of routine tasks each day, and if the store is small you may have half a real job to do (maybe ordering), but as a boss your job is to look after your people, deal with emergencies and think about the future.   On a day to day basis the store should run itself - you should need to give any "orders".

I hope this helps.  Read this answer again and think about it.  Think about who you are, how you behave, and what you would do if you worked in a store and the new boss behaved like that.  Think about good bosses you have had in the past, and copy the good things they did.  Think about the bad ones, and do the opposite.

First try to find out the reason for their resentment if the reason is geniune reconsider the orders given and go for a subtitute option otherwisw take neccesary disciplinary action against the staff disobeying.

Thanks for your nice question. You should arrange a meeting with them to discus about your store. And you will ask them how can you develop the storing system? You shouldn't only discus about official activities. You will discus about your personal life, their personal life. That means you try to free with them. After completing the meeting don't forget to serve them some snacks. 

maintain a friendly relationship with the employees and try to motivate the employees