If you are applying under the federal skilled worker program, you have to apply under 8222 because that is the one that is on the list of 38, see http://www.cic.gc.ca/english/immigrate/skilled/apply-who-instructions.asp#list
They will give you 3 years experience because 8412 is not skilled and can not be counted for points.
Look at http://www.cic.gc.ca/english/immigrate/skilled/apply-who-instructions.asp#list again. This is the list of 38 most wanted. 8412 is not on that list.
Then look at http://www.cic.gc.ca/english/immigrate/skilled/factor-experience.asp especially where it says:
Your work experience must be in the category of Skill Type 0, or Skill Level A or B on the Canadian National Occupational Classification (NOC). See below for instructions on determining the NOC category for your work experience.
This means that 8412 is in fact a C skill level occupation and therefore can not be counted for points. You can apply under 8222 and you will get points for 3 years experience unless you have some other skilled jobs in your past that you also want to add in which case you might be able to get more points.
appreciate your help leon ,but you made me confused ,i had sent my file and i got file number and i put 8412 in the top of my work experiences and 8222 the second in the application .
All jobs can be found in the NOC but only the skilled jobs, skill type 0 or skill level A or B can help you with immigration. A skill level C or D job does not help you with immigration at all, not for points or anything else.