Find specific transaction in merkel's tree We know the merkel tree is branchs of transaction hash so that root of tree is hash that show in block header. If i want to find a specific transaction, how i can?
In order to verify if a transaction is part of a merkle tree, you have to calculate the hash of the transaction id and it's sibling, and verify that the value is correct. For example,

Merkle Verification

We’ll start with a simple 2 leaf example (see the First Bitcoin Transaction):



Lets assume that hashes Ha and Hb have already been calculated from the data Ta and Tb and that:

Ha = b1fea52486ce0c62bb442b530a3f0132b826c74e473d1f2c220bfa78111c5082
Hb = f4184fc596403b9d638783cf57adfe4c75c605f6356fbc91338530e9831e9e16


First, we must reverse the bytes (they need to be little endian) because that is how Bitcoin calculates the hashes. You can use this python script, if you like:

#!/usr/bin/env python
line = raw_input("Input original hex string\n")
n = 2
orig_list = [line[i:i+n] for i in range(0, len(line), n)]
reversed_list = orig_list[::-1]
reversed = ''.join(reversed_list)
print reversed


We get:

Ha = 82501c1178fa0b222c1f3d474ec726b832013f0a532b44bb620cce8624a5feb1
Hb = 169e1e83e930853391bc6f35f605c6754cfead57cf8387639d3b4096c54f18f4


Then, the node (and root in this case) Hab is calculated by concatenating the two and hashing with sha256 twice (i.e. hash256):

$ printf "82501c1178fa0b222c1f3d474ec726b832013f0a532b44bb620cce8624a5feb1169e1e83e930853391bc6f35f605c6754cfead57cf8387639d3b4096c54f18f4" | xxd -r -p | openssl sha256
(stdin)= a24ee7fb7333f85c16560ed8850a1773d6977ce7a4936367eaf72f8fff33797e
$ printf "a24ee7fb7333f85c16560ed8850a1773d6977ce7a4936367eaf72f8fff33797e" | xxd -r -p | openssl sha256
(stdin)= ff104ccb05421ab93e63f8c3ce5c2c2e9dbb37de2764b3a3175c8166562cac7d


Now, reverse the bytes! (back to big endian):

7dac2c5666815c17a3b36427de37bb9d2e2c5ccec3f8633eb91a4205cb4c10ff


https://medium.com/coinmonks/how-to-manually-verify-the-merkle-root-of-a-bitcoin-block-command-line-7881397d4db1