In most refrigerators there will be a sticker located towards the top of the fridge compartment. Most often on the left.
Sometimes it is hard to see the numbers clearly, a good way to get a better angle on it is to take a picture with your phone.
If your stove has a pan drawer at the bottom: there will often be a sticker on the inside of the drawer, or on the facing where the drawer would shut against.
Some units will have a sticker on the back, possibly under a metal tab.
Open the door to your unit. There will likely be a sticker along where the door closes against, or along the edge of the door itself. Sometimes the sticker will be in the microwave compartment, or on the bottom of the unit.
Open your dishwasher and look at the edge where the door will seal against. There should a a sticker somewhere along that edge at the top or sides.
Locating Your Model # and Serial #
Top Loader: Raise the lid and look at the back edge of the washer top, almost under the hinges. There could also be a sticker on the back of the unit.
Front Loader: Open the door and there should be sticker either along the side of the door, or along the facing where the unit would shut against.
There will be a sticker either on the back of the unit or on the facing where the door would shut against.