Im hapi I passed my probation,how can I respond to my supervisor to thank her for the memo I recieved.?

Im hapi I passed my probation,how can I respond to my supervisor to thank her for the memo I recieved.She actually stated that I must be corfirmed to continue with employment.She wrote to the HR.And now I recieved a letter of emploment,guys I wanna write to my supervisor atleast two lines to thank her,is it adviseable and what can I write,Help me out to write guys.|||i have never been 2 jail