addons disappear from sims 3 store and launcher' stuffs don't appear in game.

lilalilacly  The merge may be the issue.  Please contact EA customer support, again, and say that you're missing certain packs after the merge.  Support may not be able to add back the Store worlds, unfortunately, although you might get a refund on the SimPoints you spent on some of them, if you ask nicely and find a person who understands the issue.

A support rep absolutely can remove and add back any expansion or stuff packs you owned as long as you can prove your previous ownership, and the packs weren't removed for fraud or similar.

I would strongly suggest using the live chat option rather than email.  If you don't see it, try this link:

https://help.ea.com/en/help-contact-us/?product=the-sims-3&topic=missing-game&category=manage-my-account&subcategory=find-missing-game

Make sure you're signed into an EA site (this one is fine) before clicking the link and that the location in the lower-right corner of the browser window is set to U.S. or U.K.

Alternately, try using the help site without being signed in.  Some categories of issue allow you to proceed without an active login, and many of those offer the live chat option.

(updated)

I already contact EA Help for the issue. after I check on sims 3 store again last hour, it has all my addons back. But the next issue is my hidden spring world has no download button but only show purchase button. So, EA said I need to purchase it again 😥.

Hey there,

Was Hidden Springs originally purchased on your older account? Prior to merging two accounts, you would get a disclaimer that mentions any content purchased from The Sims 3 store would not transfer over- that does include any purchased worlds. You would need to re-purchase Hidden Springs on your new EA account in order to access that world again.