Design 3D models ready for 3D printing

I am working on a personal project and I would like to have 5 pieces designed if possible. I also want a bigger piece designed for printing, but to start off with I want to do the pieces. All 5 pieces I would like a medieval theme for. The 5 pieces are as follows: 1. Battering Ram - L 2cm, W 1cm, H 1cm 2. Catapult - L 2cm, W 1cm, H 1cm 3. Ballista - L 2cm, W 2cm, H 1cm 4. Trebuchet - L 3cm, W 2cm, H 1cm 5. Siege Tower - L 5cm, W 1cm, H 1cm For 1 - 4 I want the view to be from the top and for 5 I would want the Siege Tower to have the view from the front. I have attached basic pictures for all 5 items for reference for you. Once the basic design is done I would also like to add some detail to pieces, pins at the bottom and holes at the top. The same design as the ships on Battleship (the board game). The pins and holes needed are as follows: 1. Battering Ram - 2 pins at the bottom and 2 holes at the top 2. Catapult - 2 pins at the bottom and 2 holes at the top 3. Ballista - 4 pins at the bottom and 4 holes at the top 4. Trebuchet - 4 pins at the bottom and 6 holes at the top 5. Siege Tower - 2 pins at the bottom and 5 holes at the top All the holes on top of the pieces are supposed to be in the middle of each cm of the piece, e.g. on the Ballista, there should be 2 holes across the length and 2 holes across the width, giving a total of 4 holes. The holes needs to be 2mm across and 3mm deep. The pins at the bottom will also be 2mm across each and 3mm long standing out from the bottom of the pieces. The location of these pieces will be allocated at the same locations as the holes on the ends of the pieces. Almost similar to a piece of Lego brick. All of these need to in an CAD file format ready for 3D printing.