Command to replace all blocks of one type with another [duplicate]

Use the /fill command.

Note the coordinates of one of the corners of your building and the one diagonally opposed:

Then use them in your command:

/fill x y z x2 y2 z2 <block> <block variant> replace <block> <block variant>

• x y z are the coords of the first corner
• x2 y2 z2 are the coords of the other corner
• the first block takes the block you want to have (use air to simply remove blocks)
• the second block is the one you want to be replaced with the first one
• replace is the magic part telling minecraft to replace blocks

So in your case this should do:

/fill x y z x2 y2 z2 planks 5 replace purpur_block
/fill x y z x2 y2 z2 log2 1 replace purpur_pillar