Creating DIY Power Bank Using 3 Samsung Galaxy S3 3.7V Batteries: Steps & Converters Needed

Hello, as in the subject. I mean, I have 3 3.7V batteries for my Samsung Galaxy S3 (they are identical) and I would like to do something with them. I know that if I connected them in parallel, I would get the same voltage, but higher capacity. Could someone show if I could do it? If necessary, I can send a photo of what the battery contacts look like. And I have a question what else would be needed, a converter?
Please help. Best regards.

There are two options:
1. You connect the pros and cons (parallel connection), you do NOT make a short circuit only 1 + to 2 + and 1 - to 2 - and properly connect to the connector on the phone (just make no mistake because it may damage the phone!). However, keep in mind that such a "battery" will be too large and will have to be outside the phone housing.

2. You connect the batteries as above (in parallel), connect to their outputs a step-up converter with output voltage. 5V (eg Pololu S7V7F5, can be found in a well-known robotics shop). You connect the inverter output to the appropriate USB connector cables (such as in the phone charger). NOTE: do not make a mistake when connecting to the connector, I burned the phone once! In addition to this, there is also a charger for these cells, read:
https://www.elektroda.pl/rtvforum/topic2625222.html
https://www.elektroda.pl/rtvforum/topic1449911.html

I advise against the former, it is only a capacity extension, and a typical powerbank is option 2.

I assume you can solder and have a basic knowledge of electronics.

I understand, someone else could tell me how can I connect such batteries? Yes, plus to plus minus to minus and it will be in parallel, but here are 4 contacts and I don't quite know how, and the question is how to connect it?
Edit: foto

Even in this photo you can see that the + and - contacts are marked. Plus is the first from the right when looking at the photo and the minus is third from the right, to be sure check with the meter you have, the others are checking the status and charging of the battery. If you want to charge such a package with a phone that they fit, you need to solder it so that it enters the phone (little tin and thin wires or a copper ribbon). And as with any other charger, remember that by charging with too much current, the electronics inside the battery can cut off the charging.

Thank you for your help, I'll try to insert after doing it?