"How many inches is the length of the side of this book?"
Translation:Berapa inci panjang sisi buku ini?
"ada" can have one of these meanings : "to be present", "to be available", "to be there", "there are", "to have".
"ada" is usually translated as "to be" or "to have".
You cannot use "ada" in the above sentence.
You would be asking about "the presence" of a length (a measurement).
See the following topic("ada"):
Remember that an Indonesian sentence doesn't necessarily need a verb in order to be a complete sentence.
The above ID sentence doesn't have a verb.
Maybe that causes the confusion.
In English, a sentence like this needs a linking verb.
If you want to use a verb, then you could use "adalah".
When using "adalah", it would be something like this:
Panjangnya sisi buku ini (adalah) dua puluh senti.
Panjangnya sisi buku ini (adalah) berapa senti ?
Berapa senti (adalah) panjangnya sisi buku ini ?
"adalah" is optional in all the above sentences (again no need for a verb).
"senti" = short form of "sentimeter" (we don't use inches in Indonesia).
See the following topic("adalah"):
Would it mean something else to say "Berapa inci panjang di sisi buku ini?"
Your Indonesian sentence is not correct because of the use of "di".
"di" is a preposition indicating a static location ('in', 'at', 'on') (there is no movement).
"dari", "ke", are locative prepositions indicating direction and/or movement ('from', 'to').
The above question ("berapa...panjang...") is about length/size, not about location, so there is no need to use these locative prepositions.
You can use these prepositions like this:
Berapa semut berjalan di sisi buku ini, dari kiri ke kanan ?
How many ants walk on the side of this book, from left to right ?
"di" is now used to indicate a static location where the ants are walking (di sisi buku ini = on the side of this book).
"dari" , "ke", are used to indicate the direction of the movement.