Assure (verb)
to tell someone confidently that something is true, especially so that they do not worry (आश्वासन देना/ विश्वास दिलाना/ भरोसा देना/ आश्वस्त करना)
She assured me that the house would not flood.
Ensure (verb)
to make sure of something/ to make something certain to happen (पक्का करना/ सुनिश्चित करना(
The company's sole concern is to ensure the safety of its employees.
Insure (verb)
to buy an insurance policy/ secure or protect someone against (a possible contingency) (बीमे से सुरक्षित करना/ बीमा करना)
She is glad the house was insured against flood damage.