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The Dutch government provides the following Visa Advisor tool to determine what visa you need. AFAIK there is no special visa category for conferences and you most likely need to apply for general Short-Stay Visa.
The online application form requires a sign-up but is then supposed to guide you which documentation is applicable to your situation. It should save your draft application and allow you to resume and complete the application at a later time when you don't have all relevant documents at hand yet.
The generic checklist is this one :
You must submit a passport or other travel document issued within the last 10 years. This must have at least 2 blank pages and be valid for at least another 3 months after the date you intend to leave the Schengen area.
You must submit a completed and signed visa application form. Each person travelling with you on your travel document must submit their own visa form. Forms for children under the age of 18 need to be signed by a parent or guardian.
If you are under 18 and are travelling without one or both of your parents or guardians, ask them to sign a consent form. Border guards may ask to see this form when you arrive in the Netherlands.
In a country where visa applications are processed by an external service provider, in most cases your digital photo will be taken at the Visa Application Centre. In all other cases you yourself will have to submit a photo with your application. This photo must meet Dutch requirements for passport photos.
When you submit your application your fingerprints will be taken. These will remain valid for 59 months. Some applicants, such as children under the age of 12, do not need to have their fingerprints taken.
Did you provide biometric data (fingerprints and photo) within the last 59 months prior to your current application? Then you can choose to have someone else submit your application for you. You do not have to appear in person. This also applies if you had your fingerprints taken within the last 59 months for a visa application submitted through another Schengen member state.
Please note that if, during the assessment of your application, it appears that your fingerprints are not in the system, you will have to come and submit them. Also, you can always be invited for an interview if your application gives reason to do so.
Note that at the moment there are still COVID-19 travel restrictions independent of Visa requirements. One of which is the EU entry ban that applies to travellers who live outside the EU/Schengen area. You may require to show proof of vaccination/recovery or maybe negative PCR test taken shortly before boarding.