In English, are contracts to 're. Technically, you can use a contraction wherever you might normally use the full, written out word. However, you should be very careful when doing this. Contractions are:

• Informal : While contractions can be very useful in written English, many experts caution against the use of contractions in formal communication. Since contractions tend to add a light and informal tone to your writing, they are often inappropriate for academic research papers, business presentations, and other types of official correspondence.

• Sometimes hard to distinguish from other words in the sentence: Saying "Where're" out loud leads to something along the lines of where-er. As "where're" is not a common contraction, many people will have trouble understanding.

• Used more for speaking: Since contractions are, as mentioned above, informal, they tend to be used more in speech. Because of this, you may not want to use "here're" and "where're" because they are hard to pronounce and differentiate from other words in the sentence.

In short, you can use those contractions, and you can technically affix "'re" to any word which is followed by are. However, use caution for the reasons above.