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Try googling food label vocabulary. Here are some I found.

http://www.survivingnjapan.com/2012/04/ultimate-guide-to-reading-food-labels.html?view=flipcard https://cotoacademy.com/japanese-food-label-vocabulary-guide/ https://kokorocares.com/blogs/blog/reading-labels-in-japan-labels-for-fresh-food

手紙 is the direct object. 家 is the place it was sent to, so I suppose that counts as an indirect object. Sentence order for Japanese is very flexible (although the verb must always come last), so I wouldn’t worry too much about memorizing any particular order beyond Subject-Object-Verb.

Edit: I took a look at the source you gave, and I think you should probably disregard this sentence pattern. It’s clear from the purpose of the lesson that they were purposefully trying to shoehorn から, へ, and に into single sentence. I don’t think it sounds particularly natural.

!japaneselanguage@sopuli.xyz is more active. It’s a community for discussion of the Japanese language rather than just learning and study methods, but plenty of the posts are about learning.