You need to clone the gazebo models from px4 and the drone gate repository
cd $HOME
git clone https://github.com/PX4/PX4-SITL_gazebo.git
git clone https://github.com/pedrogasg/drone-gate.git drone_gate
If the GAZEBO_MODEL_PATH is defined
export GAZEBO_MODEL_PATH=${GAZEBO_MODEL_PATH}:$HOME/PX4-STIL_gazebo/models:$HOME/drone_gate/models
and if is not defined
export GAZEBO_MODEL_PATH=$HOME/PX4-SITL_gazebo/models:$HOME/drone_gate/models
once the models are in the path you can use the world warehouse
gazebo drone_gate/worlds/warehouse.world
or add more gates
<include>
<name>drone_gate</name>
<uri>model://drone_gate</uri>
<pose>0 0 0 0 0 0</pose>
</include>